Uxcel - The easiest way to learn UX/UI design
Axure - The most powerful way to plan, prototype and hand off to developers, all without code. Download a free trial and see why professionals choose Axure RP 9.
uxtoast: Learn UX Design - Become familiar with design laws and learn how to use them.
Balsamiq - Balsamiq. Rapid, effective and fun wireframing software.
Awwwards Academy - Leading thinkers teach digital talent on awwwards academy
Moqups - The most stunning HTML5 app for creating resolution-independent SVG mockups, wireframes & interactive prototypes for your next project